It is known that in the field of clinical laboratory testing, in particular, blood coagulation fibrinolytic testing, D-dimer is measured. D-dimer is one type of blood coagulation molecular marker, and it is important to measure this when diagnosing various types of thrombosis which enhance the coagulation/fibrinolytic system, and DIC (disseminated intravascular coagulation syndrome), and when gaining a barometer for determining the pathosis of these and judging the effects of curing.
There are various known methods of measuring D-dimer and reagents for assaying D-dimer are also marketed. The reagents for assaying D-dimer in which one type of monoclonal antibody is sensitized to carrier particles are described in Japanese Patent Application Publication (JP-B) No. 7-46104, Japanese Patent Application Laid-Open (JP-A) No. 2000-193663; JP-A No. 2006-105633, JP-A No. 2006-234676, and Japanese Patent No. 3857468.
In diagnosis by exclusion of deep venous thrombosis, it is known that measurement of the concentration of D-dimer is useful (US2004029286 and US2009305301). In the case where a cutoff value is set for the concentration of D-dimer and the concentration of D-dimer of a subject is below the cutoff value, the subject can be determined not to have deep venous thrombosis. Therefore, there is a need for high measurement sensitivity of D-dimer in a low-density region in order to determine whether the subject has deep venous thrombosis.
In the past, the concentration of an antibody to D-dimer in an assay reagent has been improved or a sensitizer has been added into the reagent in order to improve measurement sensitivity of D-dimer. However, these methods have caused problems that background increases and a reaction solution is thickened and foamed.